Tomato Inducer of CBF Expression 1 (SlICE1) is Involved in Cold and Salt Stress Signaling

Aims: Inducer of CBF Expression 1 (ICE1), which is one of basic Helix-Loop-Helix type transcription factors, has important roles in regulation of cold stress-indiced genes of plants. Sample: To investigate functions of tomato ICE1 in cold and salt tolerance, c index (SI), immunochemical assay of endogenous ICE1 protein and RT-PCR of cold-inducible genes were conducted with tomato plants.

Methodology: Tomato plants grown for 4 weeks were subjected to cold (4ºC) and salt (0.2 M NaCl) in the presence or the absence of cell signaling inhibitors. An antibody was raised against ICE1 specific epitoipe. Immunoblot with the anti-ICE1 antibody was carried out with extractions of tomato plants treated by cold and salt stresses. The expression profiles of tomato ICE1 (SlICE1) and other cold-inducible genes including LeCBF1/2/3 and SlTPS1 were analyzed by semi-quantitative RT-PCR.

Results: An ICE1-related protein with molecular masses of approximately 55 is induced in tomato plant under chilling and salt stresses. The expression of a tomato ICE1 gene (SlICE1) under chilling stress was maintained at a constant level in contrast to the protein level. Chilling stress sequentially upregulated tomato CBF homolog, SlCBF1 and trehalose-6-phosphate synthase (SlTPS1). Based on the whole genome database of tomato, cis-elements potentially binding to ICE1 and CBF were located in upstream sequences in promoter regions of SlCBF1 and SlTPS1, respectively.

Conclusion: Tomato ICE1 homolog mediates the expression of SlCBF1in a cold-stress-induced transcription factor cascade via binding to ICE1-specific cis-elements, leading to induction of cold tolerance by trehalose synthesis